Liquid ejecting head, liquid ejecting apparatus, and piezoelectric element

ABSTRACT

A liquid ejecting head includes a piezoelectric element having a first electrode on a vibration plate, a piezoelectric layer on the first electrode, and a second electrode on the piezoelectric material layer. The piezoelectric layer has functional portions sandwiched between the first and second electrodes; the second electrode configures a common electrode provided continuously across a plurality of the functional portions; the piezoelectric layer extends to an outer side of an end of the first electrode; the vibration plate has a first region opposing the first electrode, a second region opposing an area of the piezoelectric layer extending further toward an outer side than the first electrode, and a third region further toward the outer side than the piezoelectric layer; the second region has a thickness substantially equal to or greater than the thickness of the first region; and the third region is thinner than the first region.

BACKGROUND

1. Technical Field

The present invention relates to liquid ejecting heads and liquidejecting apparatuses that eject a liquid from a nozzle by causing apiezoelectric element to deform, and particularly relates topiezoelectric elements.

2. Related Art

A liquid ejecting head that ejects liquid droplets from nozzles thatcommunicate with corresponding pressure generation chambers by causingpiezoelectric elements (piezoelectric actuators) to deform and producepressure variations in the liquid within the pressure generationchambers is known. An ink jet recording head that ejects ink droplets asthe liquid droplets can be given as a representative example thereof.

Such an ink jet recording head includes piezoelectric actuators, servingas piezoelectric elements, on, for example, one surface side of a flowchannel formation plate in which the pressure generation chambers thatcommunicate with nozzle openings is provided, and the ink droplets areejected from the nozzles by driving the piezoelectric actuators, causinga vibration plate to deform, and producing pressure changes in thepressure generation chambers.

The piezoelectric actuators are each configured of a first electrode, apiezoelectric material layer, and a second electrode provided on thevibration plate (see, for example, JP-A-2009-172878).

A configuration in which a region of the piezoelectric material layersandwiched between the first electrode and the second electrode servesas a functional portion, and the second electrode serves as a commonelectrode that is shared by a plurality of functional portions by beingprovided continuously across the plurality of functional portions, hasalso been disclosed.

However, there is demand for further improvement in the displacementproperties of a piezoelectric element configured with the secondelectrode serving as a common electrode.

It should be noted that these problems are not limited to ink jetrecording heads, and are also present in other liquid ejecting headsthat eject liquids aside from ink.

SUMMARY

It is an advantage of some aspects of the invention to provide a liquidejecting head, a liquid ejecting apparatus, and a piezoelectric elementthat improve displacement properties by suppressing breakdowns such ascracking and the like.

A liquid ejecting head according to an aspect of the invention includesa piezoelectric element having a first electrode provided on a vibrationplate, a piezoelectric material layer provided on the first electrode,and a second electrode provided on the piezoelectric material layer.Here, the piezoelectric material layer has a plurality of functionalportions sandwiched between the first electrode and the secondelectrode; the second electrode configures a common electrode providedcontinuously across a plurality of the functional portions; thepiezoelectric material layer is provided so as to extend to an outerside of an end portion of the first electrode; the vibration plate has afirst region opposing the first electrode, a second region that opposesan area of the piezoelectric material layer that extends further towardan outer side than the first electrode, and a third region providedfurther toward the outer side than the piezoelectric material layer; thesecond region has a thickness that is substantially equal to or greaterthan the thickness of the first region; and the third region is thinnerthan the first region.

According to this aspect, displacement properties of the piezoelectricelement can be improved by setting the vibration plate to be thinner atthe third region than at the first region. In addition, breakdowns suchas cracking can be suppressed from occurring in the vibration plate whenthe piezoelectric element deforms by setting the vibration plate to besubstantially the same thickness as or a greater thickness at the secondregion than the thickness at the first region.

Here, the vibration plate may have a first vibration plate and a secondvibration plate provided on the side of the first vibration plate onwhich the first electrode is located.

In addition, it is preferable for a difference in the thickness of thesecond vibration plate at the second region relative to the first regionto be no greater than 10% of the thickness of the second vibration plateat the first region. According to this configuration, the vibrationplate can be suppressed from breaking down at the second region.

In addition, it is preferable for the thickness of the second vibrationplate at the third region to be 20 to 80% the thickness of the secondvibration plate at the first region. According to this configuration,the displacement properties of the piezoelectric element can be improvedwith certainty.

Furthermore, another aspect of the invention is a liquid ejectingapparatus including the liquid ejecting head according to theaforementioned aspects.

According to this aspect, a liquid ejecting apparatus including apiezoelectric element that suppresses breakdowns and improvesdisplacement properties can be realized.

A piezoelectric element according to another aspect of the inventionincludes a first electrode provided on a vibration plate, apiezoelectric material layer provided on the first electrode, and asecond electrode provided on the piezoelectric material layer. Here, thepiezoelectric material layer has a plurality of functional portionssandwiched between the first electrode and the second electrode; thesecond electrode configures a common electrode provided continuouslyacross a plurality of the functional portions; the piezoelectricmaterial layer is provided so as to extend to an outer side of an endportion of the first electrode; the vibration plate has a first regionopposing the first electrode, a second region that opposes an area ofthe piezoelectric material layer that extends further toward an outerside than the first electrode, and a third region provided furthertoward the outer side than the piezoelectric material layer; the secondregion has a thickness that is substantially equal to or greater thanthe thickness of the first region; and the third region is thinner thanthe first region.

According to this aspect, displacement properties of the piezoelectricelement can be improved by setting the vibration plate to be thinner atthe third region than at the first region. In addition, breakdowns suchas cracking can be suppressed from occurring in the vibration plate whenthe piezoelectric element deforms by setting the vibration plate to besubstantially the same thickness as or a greater thickness at the secondregion than the thickness at the first region.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is an exploded perspective view of a recording head according toa first embodiment of the invention.

FIGS. 2A and 2B are a plan view and a cross-sectional view,respectively, of a recording head according to the first embodiment ofthe invention.

FIGS. 3A and 3B are cross-sectional views of a recording head accordingto the first embodiment of the invention.

FIG. 4 is a graph illustrating a thickness of a vibration plate and adisplacement rate according to the first embodiment of the invention.

FIGS. 5A to 5C are cross-sectional views illustrating a method formanufacturing a recording head according to the first embodiment of theinvention.

FIGS. 6A to 6E are cross-sectional views illustrating a method formanufacturing a recording head according to the first embodiment of theinvention.

FIGS. 7A to 7C are cross-sectional views illustrating a method formanufacturing a recording head according to the first embodiment of theinvention.

FIGS. 8A to 8C are cross-sectional views illustrating a method formanufacturing a recording head according to the first embodiment of theinvention.

FIG. 9 is a schematic diagram illustrating a liquid ejecting apparatusaccording to an embodiment of the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, embodiments of the invention will be described in detailwith reference to the drawings.

First Embodiment

FIG. 1 is a perspective view of an ink jet recording head serving as anexample of a liquid ejecting head according to a first embodiment of theinvention, FIGS. 2A and 2B are a plan view and a cross-sectional view,respectively, of the ink jet recording head, and FIGS. 3A and 3B arecross-sectional views illustrating primary components in an enlargedmanner.

As shown in the drawings, pressure generation chambers 12 are formed ina flow channel formation plate 10 provided in an ink jet recording headI serving as an example of the liquid ejecting head according to thisembodiment. The pressure generation chambers 12, which are defined by aplurality of partition walls 11, are arranged along a direction in whicha plurality of nozzle openings 21 that eject ink of the same color arearranged. Hereinafter, this direction will be referred to as an“arrangement direction of the pressure generation chambers 12” or a“first direction X”. The pressure generation chambers 12 are arranged inthe flow channel formation plate 10 in a plurality of rows in the firstdirection (two rows, in this embodiment). The direction in which theplurality of rows of the pressure generation chambers 12, which areformed along the first direction X, are arranged will be referred tohereinafter as a “second direction Y”.

Furthermore, ink supply channels 13 and communication channels 14 aredefined by a plurality of partition walls 11 on one end side in thelengthwise direction of the pressure generation chambers 12 in the flowchannel formation plate 10, or in other words, on one end side in thesecond direction Y that is orthogonal to the first direction X. Acommunication portion 15 that configures part of a manifold 100 isformed on an outer side of the communication channels 14 (that is, theopposite side in the second direction Y to the side on which thepressure generation chambers 12 are located), the manifold 100 servingas an ink chamber (a liquid chamber) that is common for all of thepressure generation chambers 12. In other words, liquid flow channelsconfigured of the pressure generation chambers 12, the ink supplychannels 13, the communication channels 14, and the communicationportion 15 are provided in the flow channel formation plate 10.

A nozzle plate 20 in which the nozzle openings 21 that communicate withcorresponding pressure generation chambers 12 are provided is affixed,using an adhesive, a thermally-welded film, or the like, to one surfaceside of the flow channel formation plate 10, or in other words, to asurface on which the liquid flow channels including the pressuregeneration chambers 12 and the like are open. In other words, the nozzleopenings 21 are arranged in the nozzle plate 20 in the first directionX.

A vibration plate 50 is formed on the other surface side of the flowchannel formation plate 10. The vibration plate 50 according to thisembodiment includes an elastic film 51 formed on the flow channelformation plate 10 and serving as a first vibration plate, and aninsulator film 52 formed on the elastic film 51 and serving as a secondvibration plate. Note that the liquid flow channels including thepressure generation chambers 12 and the like are formed throughanisotropic etching from one surface of the flow channel formation plate10, and the vibration plate 50 (the elastic film 51) configures theother surface of the liquid flow channels including the pressuregeneration chambers 12 and the like.

Piezoelectric elements 300 configured of a first electrode 60 having athickness of, for example, approximately 0.2 μm, a piezoelectricmaterial layer 70 having a thickness of, for example, approximately 1.0μm, and a second electrode 80 having a thickness of, for example,approximately 0.05 μm are formed upon the insulator film 52. Thepiezoelectric elements 300 provided on this plate (the flow channelformation plate 10) serve as an actuator apparatus according to thisembodiment.

Although this embodiment illustrates a configuration in which the firstelectrode 60 is provided on a plate (the flow channel formation plate10) with the vibration plate 50 therebetween, the invention is notparticularly limited thereto, and the first electrode 60 may be provideddirectly on the plate without providing the vibration plate 50. In otherwords, the first electrode 60 may act as a vibration plate. That is, “onthe plate” refers not only to being directly on the plate but also to astate of being on (above) the plate with another member interposedtherebetween.

The piezoelectric elements 300 that configure the actuator apparatuswill be described in further detail hereinafter. FIGS. 3A and 3B arecross-sectional views of the piezoelectric actuator according to thefirst embodiment of the invention.

As shown in FIGS. 3A and 3B, the first electrode 60 that partiallyconfigures the piezoelectric elements 300 is divided into parts thatcorrespond to each pressure generation chamber 12, and this configuresindividual electrodes that are independent for each piezoelectricelement 300. The individual first electrodes 60 are formed so as to benarrower than the pressure generation chambers in the first direction Xof the pressure generation chambers 12. In other words, an end portionof each first electrode 60 is, in the first direction X of the pressuregeneration chambers 12, located on the inner side in a region opposingthe corresponding pressure generation chamber 12. Meanwhile, both endsof each first electrode 60 extend, in the second direction Y of thepressure generation chambers 12, to the outer sides of the correspondingpressure generation chamber 12. Although the material of the firstelectrodes 60 is not particularly limited as long as the material is ametal, platinum (Pt), iridium (Ir), or the like can be used favorablyfor this material.

The piezoelectric material layer 70 is provided continuously along thefirst direction X, so as to have a predetermined width in the seconddirection Y. The width of the piezoelectric material layer 70 in thesecond direction Y is greater than the length of the pressure generationchambers 12 in the second direction Y. Accordingly, the piezoelectricmaterial layer 70 is provided so as to extend, in the second direction Yof the pressure generation chambers 12, to the outer sides of thepressure generation chambers 12.

An end portion of the piezoelectric material layer 70 at one end of thepressure generation chambers 12 in the second direction Y (in thisembodiment, an ink supply channel side) is located further toward theouter side than the end portions of the first electrodes 60. In otherwords, the end portions of the first electrodes 60 are covered by thepiezoelectric material layer 70. An end portion of the piezoelectricmaterial layer 70 on the other side of the pressure generation chambers12 in the second direction Y is located further toward the inner side(that is, further toward the pressure generation chambers 12) than theend portions of the first electrodes 60.

Note that lead electrodes 90 configured of gold (Au) or the like areconnected to corresponding first electrodes 60 that extend to the outerside of the piezoelectric material layer 70. Although not shown in thedrawings, the lead electrodes 90 configure terminal portions to whichconnection wires connected to a driving circuit or the like areconnected.

Meanwhile, recess portions 71 that oppose corresponding partition walls11 are formed in the piezoelectric material layer 70. The width of therecess portions 71 in the first direction X is approximately the sameas, or wider than, the width of the partition walls 11 in the firstdirection X. Accordingly, the rigidity of areas of the vibration plate50 that oppose end portions of the pressure generation chambers 12 inthe width direction thereof (so-called “arm portions” of the vibrationplate 50) is suppressed, making it possible for the piezoelectricelements 300 to displace in a favorable manner.

A perovskite-structure crystal film (a perovskite type crystal)configured of a ferroelectric ceramic material exhibiting anelectromechanical transduction effect and formed on the first electrodes60 can be given as an example of the piezoelectric material layer 70. Aferroelectric piezoelectric material such as lead zirconate titanate(PZT), a material obtained by adding a metal oxide such as niobiumoxide, nickel oxide, magnesium oxide, or the like thereto, or the likecan be used as the material of the piezoelectric material layer 70. Tobe more specific, lead titanate (PbTiO₃), lead zirconate titanate(Pb(Zr,Ti)O₃), lead zirconate (PbZrO₃), lead lanthanum titanate((Pb,La),TiO₃), lead lanthanum zirconate titanate ((Pb,La)(Zr,Ti)O₃),lead magnesium niobate zirconium titanate (Pb(Zr,Ti)(Mg,Nb)O₃), or thelike can be used. In this embodiment, lead zirconate titanate (PZT) isused for the piezoelectric material layer 70.

The material of the piezoelectric material layer 70 is not limited to alead-based piezoelectric material containing lead, and a lead-freepiezoelectric material that does not contain lead can be used as well.Bismuth ferrite ((BiFeO₃), abbr. “BFO”), barium titanate ((BaTiO₃),abbr. “BT”), potassium sodium niobate ((K,Na)(NbO₃), abbr. “KNN”),potassium sodium lithium niobate ((K,Na,Li)(NbO₃)), potassium sodiumlithium niobate tantalate ((K,Na,Li)(Nb,Ta)O₃), bismuth potassiumtitanate ((Bi_(1/2)K_(1/2))TiO₃, abbr. “BKT”), bismuth sodium titanate((Bi_(1/2)Na_(1/2))TiO₃, abbr. “BNT”), bismuth manganate (BiMnO₃, abbr.“BM”), complex oxides containing bismuth, potassium, titanium and ironand having a perovskite structure (x[(Bi_(x)K_(1-x))TiO₃]−(1−x)[BiFeO₃],abbr. “BKT-BF”), complex oxides containing bismuth, iron, barium, andtitanium and having a perovskite structure ((1−x)[BiFeO₃]−x[BaTiO₃],abbr. “BFO-BT”), a material obtained by adding a metal such asmanganese, cobalt, chromium or the like thereto((1−x)[Bi(Fe_(1-y)M_(y))O₃]−x[BaTiO₃] (where M is Mn, Co, or Cr)), andthe like can be given as examples of lead-free piezoelectric materials.

The second electrode 80 is provided continuously on the piezoelectricmaterial layer 70 in the first direction X of the pressure generationchambers 12, and configures a common electrode that is shared by aplurality of the piezoelectric elements 300. An end portion of thesecond electrode 80 at one end side of the pressure generation chambers12 in the second direction Y is positioned further on the outer sidethan the end portion of the piezoelectric material layer 70. In otherwords, the end portion of the piezoelectric material layer 70 is coveredby the second electrode 80. An end portion of the second electrode 80 onthe other side of the pressure generation chambers 12 in the seconddirection Y is located further on the inner side (that is, furthertoward the pressure generation chambers 12 side) than the end portion ofthe piezoelectric material layer 70. Although the material of the secondelectrode 80 is not particularly limited as long as the material is ametal, iridium (Ir) or the like can be used favorably for this material.

The piezoelectric element 300 configured in this manner displaces when avoltage is applied between the first electrode 60 and the secondelectrode 80. In other words, piezoelectric strain is produced in thepiezoelectric material layer 70 sandwiched between the first electrode60 and the second electrode 80 when a voltage is applied between the twoelectrodes. The area of the piezoelectric material layer 70 where thepiezoelectric strain occurs when the voltage is applied between the twoelectrodes is referred to as a “functional portion 320”. On the otherhand, the area of the piezoelectric material layer 70 where thepiezoelectric strain does not occur is referred to as a “non-functionalportion”. In the functional portion 320 where piezoelectric strainoccurs in the piezoelectric material layer 70, an area opposing thepressure generation chamber 12 is referred to as a “flexible portion”,whereas areas on the outer sides of the pressure generation chamber 12are referred to as “non-flexible portions”.

In this embodiment, the first electrode 60, the piezoelectric materiallayer 70, and the second electrode 80 are all provided continuously tothe outer sides of the corresponding pressure generation chamber 12 inthe second direction Y of the pressure generation chambers 12. In otherwords, the functional portion 320 is provided continuously to the outersides of the corresponding pressure generation chamber 12. Accordingly,an area of the functional portion 320 that opposes the pressuregeneration chamber 12 for that piezoelectric element 300 serves as theflexible portion, and areas on the outer sides of the pressuregeneration chamber 12 serve as the non-flexible portions.

Note that because the first electrodes 60 are divided into parts thatcorrespond to each pressure generation chamber 12 as described above,stepped areas are formed in the piezoelectric elements 300 by the firstelectrodes 60 along the second direction Y, or in other words, along thelengthwise direction of the functional portions 320 (the seconddirection Y).

In other words, the vibration plate 50 includes, along the firstdirection X, first regions P₁ that are regions of the vibration plate 50opposing the first electrodes 60, second regions P₂ opposing areas ofthe piezoelectric material layer 70 that extend further toward the outerside than the first electrodes 60, and third regions P₃ that are regionsprovided further toward the outer side than the piezoelectric materiallayer 70.

The thickness of the vibration plate 50 at the second regions P₂ issubstantially the same as or greater than the thickness at the firstregions P₁. Here, the thickness of the vibration plate 50 refers to thethickness in a direction orthogonal to the surface of the flow channelformation plate 10 on which the vibration plate 50 is provided. In otherwords, the thickness of the vibration plate 50 is the thickness of thevibration plate 50 in the direction in which the layers of thepiezoelectric elements 300 are stacked.

As described above, the thickness of the vibration plate 50 at thesecond regions P₂ refers to the areas opposed to the regions of thepiezoelectric material layer 70 on the outer sides of the firstelectrodes 60. Note that the second regions P₂ of the vibration plate 50having substantially the same thickness as the first regions P₁ meansthat the difference in thickness of the second regions in the insulatorfilm 52, which serves as the second vibration plate of which thevibration plate 50 is partially configured, relative to the firstregions is less than or equal to 10% of the thickness of the firstregions. In other words, when the thickness of the insulator film 52 atthe second regions P₂ is taken as a thickness t₂ and the thickness atthe first regions P₁ is taken as a thickness t₁, the relationshipt₂≧0.9×t₁ is fulfilled.

Meanwhile, the thickness of the vibration plate 50 at the third regionsP₃ is lower than the thickness t₁ at the first regions P₁. In thisembodiment, it is preferable for the thickness of the insulator film 52in the vibration plate 50 at the third regions P₃ to be greater than orequal to 20% of the thickness of the insulator film 52 at the firstregions and less than or equal to 80% of the thickness of the insulatorfilm 52 at the first regions. In other words, it is preferable for athickness t₃ of the insulator film 52 at the third regions P₃ to fulfillthe relationship 0.2×t₁≦t₃≦0.8×t₁.

Here, in this embodiment, the third regions P₃ are provided opposingborder areas between the partition walls 11 in the flow channelformation plate 10 and the pressure generation chambers 12, and thusmaking the vibration plate thinner at the third regions P₃ than at thefirst regions P₁ makes it possible to reduce the rigidity of theso-called arm portions of the vibration plate 50, which are regions ofthe non-functional portion at the regions (flexible portions) thatoppose the pressure generation chambers 12; this makes it possible toimprove the piezoelectric properties. Accordingly, a large amount ofdisplacement can be obtained with a low voltage. Incidentally,increasing the thickness of the vibration plate 50 at the third regionsP₃ increases the rigidity of the arm portions and leads to a drop in thedisplacement properties.

Furthermore, setting the thickness of the vibration plate 50 at thesecond regions P₂ to the same or a greater thickness than at the firstregions P₁ makes it possible to suppress breakdowns such as cracking andthe like in the vibration plate 50 at the second regions P₂.

Displacement rates of the piezoelectric elements 300 in the case wherethe thickness t₃ of the insulator film at the third regions P₃ ischanged were measured. The results are shown in FIG. 4. Note thatdisplacement amounts were found when using a vibration plate 50 in whichthe elastic film 51 is 470 nm thick and the insulator film 52 is 150 nmthick and a voltage of 25 V was applied to the piezoelectric elements300, and FIG. 4 illustrates displacement rates as a ratio ofdisplacement amounts when the thickness of the insulator film 52 at thethird regions P₃ was changed relative to the thickness at the firstregions P₁, using the displacement amount when the thickness t₃ of theinsulator film 52 at the third regions P₃ is the same as the thicknesst₁ at the first regions P₁ as 100%.

As shown in FIG. 4, the displacement rate of the piezoelectric elements300 (the functional portions 320) can be improved, regardless of thethickness of the elastic film 51, by setting the thickness t₃ of theinsulator film 52 at the third regions P₃ to be lower than the thicknesst₁ at the first regions P₁. In particular, in the case where the elasticfilm 51 is 470 nm thick, the displacement amount can be improved byapproximately 30% by setting the thickness of the insulator film 52 atthe third regions P₃ to 20% of the thickness at the first regions P₁.

A protective plate 30 that protects the piezoelectric elements 300 isaffixed, using an adhesive 35, on the flow channel formation plate 10 inwhich the piezoelectric elements 300 are formed. A piezoelectric elementholding portion 31, which is a recess defining a space that houses thepiezoelectric elements 300, is provided in the protective plate 30.Furthermore, a manifold portion 32 that configures part of the manifold100 is provided in the protective plate 30. The manifold portion 32 isformed passing through the protective plate 30 in the thicknessdirection thereof and spanning in the width direction of the pressuregeneration chambers 12, and communicates with the communication portion15 of the flow channel formation plate 10 described above. Meanwhile, athrough-hole 33 that passes through the protective plate 30 in thethickness direction thereof is provided in the protective plate 30. Thelead electrodes 90 connected to the first electrodes 60 in therespective piezoelectric elements 300 are exposed inside thethrough-hole 33. The lead electrodes 90 connected to the correspondingfirst electrodes 60 in the piezoelectric elements 300 are exposed withinthe through-hole 33, and one end of each of the connection wiresconnected to the driving circuit (not shown) is connected to acorresponding lead electrode 90 within the through-hole 33.

A compliance plate 40, configured of a sealing membrane 41 and ananchoring plate 42, is affixed onto the protective plate 30. The sealingmembrane 41 is configured of a flexible material having a low rigidity,and one surface of the manifold portion 32 is sealed by the sealingmembrane 41. The anchoring plate 42, meanwhile, is formed of a hardmaterial such as a metal or the like. The region of the anchoring plate42 that opposes the manifold 100 has an opening portion 43 in which theanchoring plate 42 has been completely removed in the thicknessdirection, and thus one surface of the manifold 100 is sealed using onlythe flexible sealing membrane 41.

In the ink jet recording head I according to this embodiment, ink isimported from an ink introduction port connected to an external inksupply unit (not shown), and after the interior from the manifold 100 tothe nozzle openings 21 has been filled with ink, a voltage is appliedbetween the first electrodes 60 corresponding to respective pressuregeneration chambers 12 and the second electrode 80 in accordance withrecording signals from a driving circuit. As a result, the vibrationplate 50 bends and deforms along with the piezoelectric elements 300,increasing pressure within the pressure generation chambers 12 andejecting ink droplets from the nozzle openings 21.

Next, a method for manufacturing the ink jet recording head according tothis embodiment will be described. FIGS. 5A to 8C are cross-sectionalviews taken along the first direction X, illustrating a method formanufacturing the ink jet recording head.

First, as shown in FIG. 5A, the elastic film 51 is formed on a surfaceof a flow channel formation plate wafer 110, which is a silicon wafer.In this embodiment, the elastic film 51 is formed from silicon dioxideby thermally oxidizing the flow channel formation plate wafer 110. Ofcourse, the material of the elastic film 51 is not limited to silicondioxide, and a silicon nitride film, a polysilicon film, an organic film(polyimide, parylene, and so on), or the like may be used as well.Furthermore, the method for forming the elastic film 51 is not limitedto thermal oxidizing, and the elastic film 51 may be formed throughsputtering, CVD, spin coating, or the like.

Next, as shown in FIG. 5B, the insulator film 52 is formed fromzirconium oxide on the elastic film 51. Of course, the insulator film 52is not limited to zirconium oxide, and titanium oxide (TiO₂), aluminumoxide (Al₂O₃), hafnium oxide (HfO₂), magnesium oxide (MgO), lanthanumaluminate (LaAlO₃), or the like may be used as well. Sputtering, CVD,another type of vapor deposition, or the like can be given as methodsfor forming the insulator film 52.

Next, as shown in FIG. 5C, the first electrode 60 is formed on theentire surface of the insulator film 52. Although the material used forthe first electrode 60 is not particularly limited, it is desirable, inthe case where lead zirconate titanate (PZT) is employed as thepiezoelectric material layer 70, to use a material whose conductivityexperiences little change in response to the diffusion of lead oxide.Accordingly, platinum, iridium, and the like are used favorably as thematerial of the first electrode 60. In addition, the first electrode 60can be formed through sputtering, PVD (physical vapor deposition), orthe like.

Next, as shown in FIG. 6A, a crystal seed layer 61 configured oftitanium (Ti) is formed on the first electrode 60. Providing the crystalseed layer 61 on the first electrode 60 in this manner makes it possibleto control the preferred orientation direction of the piezoelectricmaterial layer 70 to (100) when forming the piezoelectric material layer70 on the first electrode 60 over the crystal seed layer 61 in a laterstep, which in turn makes it possible to obtain a piezoelectric materiallayer 70 favorable for use as an electromechanical transducer. Note thatthe crystal seed layer 61 functions as a seed for acceleratingcrystallization when the piezoelectric material layer 70 crystallizes,and diffuses into the piezoelectric material layer 70 after thepiezoelectric material layer 70 is sintered. In addition, althoughtitanium (Ti) is used for the crystal seed layer 61 in this embodiment,the crystal seed layer 61 is not particularly limited thereto as long asthe material can serve as nuclei for the crystals of the piezoelectricmaterial layer 70 when forming the piezoelectric material layer 70 inlater steps; for example, titanium oxide (TiO₂) may be used for thecrystal seed layer 61, and a material aside from titanium and titaniumoxide, such as lanthanum nickel oxide, can be used as well. Of course,the configuration may be such that the crystal seed layer 61 remainsbetween the first electrode 60 and the piezoelectric material layer 70.The crystal seed layer 61 may have a layer shape, or may have an islandshape.

Next, in this embodiment, the piezoelectric material layer 70,configured of lead zirconate titanate (PZT), is formed. Here, in thisembodiment, the piezoelectric material layer 70 is formed using what isknown as the sol-gel method, where the piezoelectric material layer 70configured of a metal oxide is obtained by applying a sol in which ametal complex has been dissolved and dispersed throughout a liquidmedium, allowing the sol to dry and turn into a gel, and then sinteringthe gel at a high temperature. However, the method for forming thepiezoelectric material layer 70 is not limited to the sol-gel method,and MOD (metal-organic decomposition), sputtering, or a physical vapordeposition (PVD) technique such as laser abrasion may be used as well.In other words, the piezoelectric material layer 70 may be formed usingeither of a liquid-phase method or a gas-phase method.

To describe a specific procedure for forming the piezoelectric materiallayer 70, first, a piezoelectric material precursor film 73, which is aPZT precursor film, is deposited upon the crystal seed layer 61, asshown in FIG. 6B. In other words, a sol (solution) containing a metalcomplex is applied to the flow channel formation plate wafer 110 onwhich the first electrode 60 (the crystal seed layer 61) has been formed(an application step). The method for applying the sol is notparticularly limited, and spin coating using a spin coat apparatus, slitcoating using a slit nozzle coater, and so on can be given as otherexamples. Next, the piezoelectric material precursor film 73 is heatedto a predetermined temperature and allowed to dry for a set amount oftime (a drying step). For example, in this embodiment, the piezoelectricmaterial precursor film 73 can be dried by being held at 170 to 180° C.for 8 to 30 minutes.

Next, the dried piezoelectric material precursor film 73 is degreased bybeing heated to a predetermined temperature and held at that temperaturefor a set amount of time (a degreasing step). For example, in thisembodiment, the piezoelectric material precursor film 73 is degreased bybeing heated to a temperature of approximately 300 to 400° C. and heldat that temperature for 10 to 30 minutes. Note that “degreasing” asdescribed here refers to separating organic components contained in thepiezoelectric material precursor film 73 as, for example, NO₂, CO₂, H₂O,or the like.

Next, as shown in FIG. 6C, a piezoelectric material film 74 is formed byheating the piezoelectric material precursor film 73 to a predeterminedtemperature and holding that temperature for a set amount of time inorder to crystallize the piezoelectric material precursor film 73 (asintering step). It is preferable to heat the piezoelectric materialprecursor film 73 to no less than 700° C. in this sintering step. Notealso that it is preferable for the rate of the rise in temperature inthe sintering step to be greater than or equal to 50° C./sec. Apiezoelectric material film 74 having superior properties can beobtained as a result.

The crystal seed layer 61 formed on the first electrode 60 diffuses intothe piezoelectric material layer 74. Of course, the crystal seed layer61 may remain as titanium between the first electrode 60 and thepiezoelectric material 74, or may remain as titanium oxide.

For example, a hot plate, an RTP (rapid thermal processing) device thatheats using an infrared lamp, or the like can be used as the heatingdevice employed in the drying step, the degreasing step, and thesintering step.

Next, as shown in FIG. 6D, at the stage where a first layer of thepiezoelectric material film 74 has been formed on the first electrode60, the first electrode 60 and the first layer of the piezoelectricmaterial film 74 are simultaneously patterned so that the side surfacesthereof are sloped. The patterning of the first electrode 60 and thefirst layer of the piezoelectric material film 74 can be carried outthrough dry etching such as ion milling.

In the case where, for example, the first layer of the piezoelectricmaterial film 74 is formed after first patterning the first electrode60, the first electrode 60 is patterned through photoprocessing, ionmilling, and ashing, and thus changes in the qualities of the surface ofthe first electrode 60, the crystal seed layer provided on that surface,and so on will result. If the piezoelectric material film 74 is thenformed on the surface whose qualities have changed, the piezoelectricmaterial film 74 will not have a favorable crystalline state; thecrystal growth in the second and subsequent layers of the piezoelectricmaterial film 74 will be affected by the crystalline state of the firstlayer of the piezoelectric material film 74 as well, and thus thepiezoelectric material layer 70 cannot be formed having a favorablecrystalline state.

However, if the first layer of the piezoelectric material film 74 isformed and then patterned simultaneously with the first electrode 60,the first layer of the piezoelectric material film 74 will have strongerqualities as a seed for favorable crystal growth in the second andsubsequent layers of the piezoelectric material film 74 than a crystalseed such as titanium; accordingly, even if an extremely thin layerwhose qualities have changed is formed on the surface layer during thepatterning, that layer will not have a large effect on the crystalgrowth in the second and subsequent layers of the piezoelectric materialfilm 74.

In addition, in this embodiment, the surface of the vibration plate 50is not etched or is etched very little when etching the first electrode60 and the piezoelectric material film 74. Accordingly, the secondregions in the vibration plate 50 can be set to substantially the samethickness as the first regions or a thickness that is greater than thethickness of the first regions, without over-etching the second regions.

Incidentally, because the first electrodes 60 function as the individualelectrodes for corresponding functional portions 320, it is necessary tocompletely divide the first electrode 60 through etching in order forthe individual first electrodes 60 to correspond to respectivefunctional portions 320. On the other hand, it is necessary to managethe thicknesses of the first electrode 60 and the piezoelectric materialfilm 74, and manage the etching time, so that the vibration plate 50 isover-etched very little, and it is difficult to etch the first electrode60 and the piezoelectric material film 74 while not etching thevibration plate 50 at all. Accordingly, in this embodiment, thevibration plate 50 is considered to have substantially the samethickness at the second regions as at the first regions even in the casewhere the difference in thickness of the insulator film 52, of which thevibration plate 50 is partially configured, at the second regionsthereof relative to the first regions is less than or equal to 10% ofthe thickness of the insulator film 52 at the first regions.

Next, as shown in FIG. 6E, after the first layer of the piezoelectricmaterial film 74 and the first electrode 60 have been patterned, anintermediate crystal seed layer 200 is formed spanning the top of theinsulator film 52, the side surfaces of the individual first electrodes60, the side surfaces of the first layer of the piezoelectric materialfilm 74, and the top of the piezoelectric material film 74. Theintermediate crystal seed layer 200 can employ titanium, lanthanumnickel oxide, or the like, in the same manner as the crystal seed layer61. Like the crystal seed layer, the intermediate crystal seed layer mayhave a layer shape, or may have an island shape.

Next, as shown in FIG. 7A, the piezoelectric material layer 70 is formedfrom a plurality of layers of the piezoelectric material film 74, whichare formed by repeating a piezoelectric material film formation processincluding the aforementioned application step, drying step, degreasingstep, and sintering step a plurality of times.

Incidentally, the second and subsequent layers of the piezoelectricmaterial film 74 are formed so as to be continuous across the top of theinsulator film 52, the side surfaces of the first electrodes 60 and thefirst layer of the piezoelectric material film 74, and the top of thefirst layer of the piezoelectric material film 74. Because theintermediate crystal seed layer 200 is formed in the regions where thesecond and subsequent layers of the piezoelectric material film 74 areformed, the preferred orientation in the second and subsequent layers ofthe piezoelectric material film 74 can be controlled to (100) by theintermediate crystal seed layer 200, and the film can be formed withextremely small particle diameters. Note that the intermediate crystalseed layer 200 functions as a seed for accelerating crystallization whenthe piezoelectric material layer 70 crystallizes, and thus may beentirely diffused into the piezoelectric material layer 70 after thepiezoelectric material layer 70 is sintered, or may partially remainas-is or as an oxidant.

Next, as shown in FIG. 7B, the piezoelectric material layer 70 ispatterned at regions opposing the respective pressure generationchambers 12. In this embodiment, the patterning is performed throughwhat is known as photolithography, in which a mask (not shown) formed ina predetermined shape is provided upon the piezoelectric material layer70 and the piezoelectric material layer 70 is etched over this mask. Dryetching such as reactive ion etching, ion milling, or the like can begiven as examples of techniques for patterning the piezoelectricmaterial layer 70. Furthermore, part of the vibration plate 50 in thethickness direction thereof is removed through over-etching when thepiezoelectric material layer 70 is etched. Accordingly, the vibrationplate 50 at the third regions can be made thinner than at the firstregions.

Incidentally, the amount of over-etching carried out when etching thevibration plate 50 can be adjusted based on the etching time. Althoughthis embodiment describes etching the piezoelectric material layer 70and part of the vibration plate 50 simultaneously through dry etching,it should be noted that the embodiment is not limited thereto, and partof the vibration plate 50 may be removed through dry etching after thepiezoelectric material layer 70 has been patterned through wet etching.

In this manner, the third regions can be formed by etching the vibrationplate 50 simultaneously with the patterning of the piezoelectricmaterial layer 70, which makes it possible to simplify the manufacturingprocess and reduce costs.

Next, as shown in FIG. 7C, the second electrode 80 is formed of, forexample, iridium (Ir) across the top of the piezoelectric material layer70 and the top of the insulator film 52, and is then patterned in apredetermined shape, forming the piezoelectric elements 300 as a result.

Next, as shown in FIG. 8A, a protective plate wafer 130, which is asilicon wafer and serves as a plurality of the protective plates 30, isaffixed to the side of the piezoelectric elements 300 of the flowchannel formation plate wafer 110 using the adhesive 35 (see FIG. 2B),after which the thickness of the flow channel formation plate wafer 110is reduced to a predetermined thickness.

Next, as shown in FIG. 8B, a masking film 53 is newly formed on the flowchannel formation plate wafer 110 and is patterned in a predeterminedshape. Then, as shown in FIG. 8C, the pressure generation chambers 12corresponding to the piezoelectric elements 300, the ink supply channels13, the communication channels 14, the communication portion 15 and thelike are formed by performing anisotropic etching (wet etching) using analkali solution such as KOH on the flow channel formation plate wafer110 over the masking film 53.

After this, unnecessary areas on the outer edges of the flow channelformation plate wafer 110 and the protective plate wafer 130 are cut offand removed through dicing or the like. The ink jet recording headaccording to this embodiment is then obtained by affixing the nozzleplate 20, in which the nozzle openings 21 are provided, to the surfaceof the flow channel formation plate wafer 110 on the opposite side tothe protective plate wafer 130, affixing the compliance plate 40 to theprotective plate wafer 130, and dividing the flow channel formationplate wafer 110 and the like into the flow channel formation plates 10having the single chip size shown in FIG. 1.

Other Embodiments

Although the invention has been described thus far according to anembodiment, the invention is not intended to be limited to the basicconfiguration described above.

For example, although the above first embodiment describes an example inwhich the piezoelectric material layer 70 for the piezoelectric elements300 is provided continuously, the piezoelectric material layer 70 may,of course, be provided independently for each piezoelectric element 300.

In addition, although the above first embodiment describes reducing thethickness of the vibration plate 50 at the third regions P₃ by reducingthe thickness of the insulator film 52 at the third regions P₃, theinvention is not particularly limited thereto; for example, thethickness of the elastic film 51, which serves as the first vibrationplate that partially configures the vibration plate 50, may be adjusted.In addition, the vibration plate 50 is not limited to being configuredof the elastic film 51 and the insulator film 52, and the vibrationplate 50 may include another film; in this case, the vibration plate 50may be made thinner at the third regions P₃ than at the first regions P₁by adjusting the thickness of that other film.

In addition, the ink jet recording head I is mounted in, for example, anink jet recording apparatus II such as that shown in FIG. 9. A recordinghead unit 1 that includes the ink jet recording head I is provided witha removable ink cartridge 2 that configures an ink supply unit, and acarriage 3 in which the recording head unit 1 is mounted is provided soas to be capable of moving in an axial direction of a carriage shaft 5attached to an apparatus main body 4. This recording head unit 1 ejects,for example, black ink compounds and color ink compounds.

Transmitting driving force generated by a driving motor 6 to thecarriage 3 via a plurality of gears (not shown) and a timing belt 7moves the carriage 3, in which the recording head unit 1 is mounted,along the carriage shaft 5. Meanwhile, a platen 8 is provided in theapparatus main body 4 along the same direction as the carriage shaft 5,and a recording sheet S, which is a recording medium such as papersupplied by paper supply rollers and the like (not shown), is wound andtransported by the platen 8.

In the invention, ejection properties can be made uniform whilesuppressing breakdowns in the piezoelectric elements 300 that configurethe ink jet recording head I as described above. As a result, the inkjet recording apparatus II, which improves printing quality and has anincreased durability, can be realized.

Although the above example describes the ink jet recording head I in theink jet recording apparatus II as being mounted in the carriage 3 andmoving in a main scanning direction, it should be noted that theconfiguration is not particularly limited thereto. For example, the inkjet recording apparatus II may be what is known as a line-type recordingapparatus, in which the ink jet recording head I is fixed and printingis carried out by moving the recording sheet S such as paper in a subscanning direction.

In addition, although the ink jet recording apparatus II is described inthe above example as being configured so that the ink cartridge 2, whichserves as a liquid holding unit, is mounted in the carriage 3, theconfiguration is not particularly limited thereto; for example, a liquidholding unit such as an ink tank may be fixed to the apparatus main body4, and the holding unit and the ink jet recording head I may beconnected via a supply pipe such as a tube. Furthermore, the liquidholding unit need not be mounted in the ink jet recording apparatus.

Furthermore, although the above embodiment describes the invention usingan ink jet recording head as an example of the liquid ejecting head, theinvention is generally applicable in all liquid ejecting heads. Varioustypes of recording heads used in image recording apparatuses such asprinters, coloring material ejecting heads used in the manufacture ofcolor filters for liquid-crystal displays and the like, electrodematerial ejecting heads used in the formation of electrodes for organicEL displays, FEDs (field emission displays), and so on, bioorganicmatter ejecting heads used in the manufacture of biochips, and so on canbe given as other examples of liquid ejecting heads.

Furthermore, the invention is not limited to piezoelectric elements usedin liquid ejecting heads, and can be applied in other devices as well.Ultrasound devices such as ultrasound wave transmitters, ultrasoundmotors, piezoelectric transformers, and the like can be given asexamples of such devices. The invention can also be applied inpiezoelectric elements used as sensors. Infrared sensors, ultrasoundsensors, thermal sensors, pressure sensors, pyroelectric sensors, and soon can be given as examples of sensors in which piezoelectric elementsare used.

The entire disclosure of Japanese Patent Application No. 2012-235423,filed Oct. 25, 2012 is expressly incorporated by reference herein.

What is claimed is:
 1. A liquid ejecting head comprising: apiezoelectric element including a first electrode provided on avibration plate, a piezoelectric material layer provided on the firstelectrode, and a second electrode provided on the piezoelectric materiallayer, wherein the piezoelectric material layer has a plurality offunctional portions sandwiched between the first electrode and thesecond electrode; the second electrode configures a common electrodeprovided continuously across a plurality of the functional portions; thepiezoelectric material layer is provided so as to extend to an outerside of an end portion of the first electrode; the vibration plate has afirst region opposing the first electrode, a second region that opposesan area of the piezoelectric material layer that extends further towardan outer side than the first electrode, and a third region providedfurther toward the outer side than the piezoelectric material layer; thesecond region has a thickness that is substantially equal to or greaterthan the thickness of the first region; and the third region is thinnerthan the first region.
 2. The liquid ejecting head according to claim 1,wherein the vibration plate has a first vibration plate and a secondvibration plate provided on the side of the first vibration plate onwhich the first electrode is located.
 3. The liquid ejecting headaccording to claim 2, wherein a difference in the thickness of thesecond vibration plate at the second region relative to the first regionis no greater than 10% of the thickness of the second vibration plate atthe first region.
 4. The liquid ejecting head according to claim 2,wherein the thickness of the second vibration plate at the third regionis 20 to 80% the thickness of the second vibration plate at the firstregion.
 5. A liquid ejecting apparatus comprising the liquid ejectinghead according to claim
 1. 6. A liquid ejecting apparatus comprising theliquid ejecting head according to claim
 2. 7. A liquid ejectingapparatus comprising the liquid ejecting head according to claim
 3. 8. Aliquid ejecting apparatus comprising the liquid ejecting head accordingto claim
 4. 9. A piezoelectric element comprising: a first electrodeprovided on a vibration plate; a piezoelectric material layer providedon the first electrode; and a second electrode provided on thepiezoelectric material layer, wherein the piezoelectric material layerhas a plurality of functional portions sandwiched between the firstelectrode and the second electrode; the second electrode configures acommon electrode provided continuously across a plurality of thefunctional portions; the piezoelectric material layer is provided so asto extend to an outer side of an end portion of the first electrode; thevibration plate has a first region opposing the first electrode, asecond region that opposes an area of the piezoelectric material layerthat extends further toward an outer side than the first electrode, anda third region provided further toward the outer side than thepiezoelectric material layer; the second region has a thickness that issubstantially equal to or greater than the thickness of the firstregion; and the third region is thinner than the first region.